Answer for what are the major reasons of declining sifs

Major reasons of declining SIS of fishes –

1. Losses of habitat
2. Losses of breeding ground
3. Losses of migratory route between habitat and breeding ground

 
You may also read –

• http://bn.bdfish.org/2011/05/বাংলাদেশ-মৎস্য-বৈচিত্র্য/
• http://bn.bdfish.org/2011/05/মৎস্যবৈচিত্র্য-হ্রাস/
• http://bn.bdfish.org/2011/07/মৎস্য-বৈচিত্র্য-রক্ষা/